At his arraignment in federal court in Tucson, Arizona, on Wednesday, he pleaded not guilty to a litany of charges, including first-degree murder. He is also charged with second-degree murder, conspiracy to interfere with commerce by robbery, attempted interference with commerce by robbery, using and carrying a firearm during a crime of violence, assault on a federal officer and possession of a firearm by a prohibited person.

The "Fast and Furious" operation of the Bureau of Alcohol, Tobacco, Firearms and Explosives began in 2009 with the purpose of tracking around 2,000 weapons intended for drug cartels. But officials couldn't track the firearms, and most are believed to have ended up with cartels and gangsters in Mexico.

"This development brings us one step closer to achieving justice for a beloved agent who paid the highest price in protecting this country," U.S. Attorney Laura E. Duffy of the Southern District of California said in a news release.

Terry was killed in a confrontation with Portillo Meza and four others along Arizona's border with Mexico on December 14, 2010.

The Terry case has been controversial because two rifles from the "Fast and Furious" operation were found at the scene of his death. But U.S. officials have not produced evidence proving that Terry was killed with either of those guns.